Posterior-segment surgical procedures include a variety of ophthalmic surgical procedures performed to treat conditions of the back of the eye, such as age-related macular degeneration (AMD), diabetic retinopathy and diabetic vitreous hemorrhage, macular hole, retinal detachment, epiretinal membrane, CMV retinitis, and others.
The vitreous is a normally clear, gel-like substance that fills the center of the eye. It makes up approximately two-thirds of the eye's volume, giving it form and shape. Certain problems affecting the back of the eye may require a vitrectomy, or surgical removal of the vitreous.
A vitrectomy may be performed to clear blood and debris from the eye, to remove scar tissue, or to alleviate traction on the retina. Blood, inflammatory cells, debris, and scar tissue obscure light as it passes through the eye to the retina, resulting in blurred vision. The vitreous is also removed if it is pulling or tugging the retina from its normal position. Some of the most common eye conditions that require vitrectomy include complications from diabetic retinopathy such as retinal detachment or bleeding, macular hole, retinal detachment, pre-retinal membrane fibrosis, bleeding inside the eye (vitreous hemorrhage), injury or infection, and certain problems related to previous eye surgery.
In a typical vitrectomy, a surgeon creates three tiny incisions in the eye for three separate instruments. These incisions are placed in the pars plana of the eye, which is located just behind the iris but in front of the retina. The instruments which pass through these incisions include a light pipe, an infusion port, and a vitrectomy cutting device.
The vitrector, or cutting device, works like a tiny guillotine, with an oscillating microscopic cutter to aspirate vitreous gel in a controlled fashion. As vitreous fluid is aspirated during posterior segment surgery, intraocular pressure drops and the eye tends to soften. The infusion port is thus used to infuse fluid (liquid and/or gas) in the eye to maintain intraocular pressure and avoid globe deformation or collapse. In addition, controlling intraocular pressure may help maintain scleral rigidity to facilitate movement of the eye and exchange of instruments during the procedure. Controlling intraocular pressure may also increase the visibility of eye tissues and reduce bleeding. However, intraocular pressure must be carefully regulated, as prolonged periods of elevated intraocular pressure can damage eye structures.
Hemorrhaging is a common problem in posterior segment surgery. Typically, a surgeon must monitor for hemorrhaging during a procedure and, in the event hemorrhaging occurs, must pause the procedure and manually adjust controls of a surgical console (e.g., via a foot pedal) to increase intraocular pressure for a period of time. Increasing intraocular pressure in this manner causes the infused fluid to act as a tamponade, compressing the hemorrhaging wound and allowing blood to clot. Once the bleeding stops, the surgeon clears the blood from the vitreous cavity and resumes the procedure.
In many cases, a surgeon may not recognize hemorrhaging until it reaches a point that blood obstructs the surgical view. This late recognition of hemorrhaging creates a situation that is dangerous for the patient, and consumes additional time in the surgical theater. Moreover, constantly monitoring for hemorrhaging is difficult and distracting for surgeon. Thus, there exists a need for improved systems and techniques to identify and respond to hemorrhaging as early as possible.